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Gynoecium

It is the most innermost whorl and the female reproductive organ of a flower. It is made up of one or more carpels. Each carpel has three parts – Stigma, Style and Ovary.

carpel-structure.jpg

Stigma

It is the topmost part of a carpel. Stigma forms the receptor surface for the pollen grains.

Style

It is the elongated tube that connects stigma and the ovary.

Ovary

  • Ovary is the basal swollen part of carpels.
  • If an ovary is formed by only one carpel, it is called mono-carpellary pistil. If it is made of two carpels, it is called bi-carpellary pistil. If it is composed of three carpels, it is called tri-carpellary, and so on.
  • If the carpels are fused together, it is called Syncarpous, and if they are free, the condition is called Apocarpous.

Placentataion

Within the ovary, ovules are developed within a special tissue called the placenta. The mode of arrangement of ovules in the placenta is known as placentation.

There are different kinds of placentation.

  1. Marginal: The placenta is formed along the wall of the ovary, forming a ridge along the ventral suture (opening) of the ovary. The ovules are found in two rows within the placenta. These are usually found in monocarpellary, unilocular ovaries. (e.g. Pisum)

placentation.jpg Marginal Placentation.png

  1. Parietal: The placenta is developed on the peripheral part of the ovary, along the inner wall. It is usually seen in bi-, or multi-carpellary, syncarpous ovaries. (e.g. Cucurbita)

parietal-axile.jpg placentation.jpg cuke-parietal.jpg

  1. Axile: The placenta is developed in the centre. Hence, the ovules are found around the central axis. It is found in bi- or multicarpellary, syncarpous ovaries. (e.g. Hibiscus)

glossIrisLutescens_OvaryXsect.jpg placentation.jpg 1086621446_64b79edd94_b.jpg pepper-axile.jpg

  1. Basal: there is a single placenta at the base of the ovary, with a single ovule. It is usually found in monocarpellary syncarpous ovaries. (e.g. Helianthus)

placentation.jpg placentation.jpg 51- Basal placentation.jpg 51- Basal placentation.jpg

  1. Free central: The ovules are developed around a central column which is not connected to the ovary. (e.g. Dianthus)

placentation.jpg free-central.jpg free-central.jpg

  1. Superficial: The placenta is formed all around the inner surface of the ovary including the septa.

28.png nym_sp_xs.jpg nym_sp_locule.jpg

 

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